Three-dimensional frequency selective surfaces

A large number of different frequency selective surface (FSS) designs have been proposed over the past four decades. Most of these designs are actually derived from the well-known traditional configuration that consists of a cascaded combination of two-dimensional (2-D) FSS and dielectric layers. Recently, an interesting concept of three-dimensional (3-D) FSS has been demonstrated to obtain superior filtering response. This 3-D FSS comprises a 2-D periodic array of multimode cavities whose coupling with air can be controlled to obtain a desired frequency response. The new approach results in an elliptical filtering performance, which was rarely found in traditional FSSs. Based on their superior features and distinct configuration, we classify them as a separate class of high performance FSS, and highlight their notable characteristics in this paper. We also present a review of the current state of the art of research work related to 3-D FSSs, and suggest a few topics for future explorations.